Two articles in this issue mark a substantial advance in our understanding of human population history in the Pacific area. On page 479, Gray et al. (1) report a computational linguistic analysis that offers a detailed and precise scenario for the dispersal and development of the Austronesian languages, and by implication of human populations among the Pacific islands. The authors come down decisively in favor of one of the two major models for the peopling of the Pacific. On page 527, Moodley et al. (2) come to the same conclusion as Gray et al. about the source and trajectory of spread of the human populations in question, based on results from a seemingly unrelated field: the archaeogenetics of human gastric bacterial parasites. In the rapidly developing field of computational historical linguistics (3), this impressive reassessment of the Pacific languages and its corroboration from a very different source are likely to have an impact in linguistic studies far beyond the Pacific area.

The reconstruction of Pacific population history, especially in Polynesia, has been a focus of archaeological interest for many years. The recognition of a characteristically decorated pottery style as a marker left by the first human inhabitants of western Polynesia is one of the contributions made by prehistoric archaeology (4). Because this pottery is associated with the first crop cultivators in the area, agricultural dispersal is often seen as a vehicle for language dispersal.

The languages of Polynesia are part of the widely distributed Austronesian language family, one of the largest language families in the world (5). Its more than 1000 constituent languages include the Micronesian and Polynesian subfamilies as well as the languages of Malaya, much of Indonesia, the Philippines, Taiwan, and Madagascar. The origin of this family has been disputed. One theory, favored by many linguists, places the homeland of the Austronesian languages in Taiwan (6), where languages of several Austronesian subfamilies are located and where farming communities existed as early as 5000 years ago. This theory envisages a farming-language dispersal from Taiwan to the Philippines and then to West Polynesia, starting around 5000 years ago. The alternate, gradualist model sees the process starting very much earlier in island Southeast Asia (7). Genetic studies have given conflicting results, and human mitochondrial DNA data do not seem to point to a Taiwanese origin for the populations that now speak Austronesian languages (8). The archaeogenetic evidence is, however, not easy to interpret, and there may have been substantial gene flow in recent colonial times (9).

Gray et al. now apply computer-based phylogenetic methods to this problem. Language trees have been a tool in historical linguistics since the 19th century (see the first figure) (10), but the computational analysis enables a more systematic investigation, which also offers a chronology for the various stages. Gray and Atkinson previously used the same method to study the Indo-European language family (11), but that analysis has not yet found favor with most historical linguists. The present analysis of the Pacific languages is, however, based on a very much larger database of more than 400 languages [compared with 87 languages in (11)]. Moreover, it relies for its lexical data on the work of Blust (12) and other linguists generally regarded as the leading authorities on the Austronesian languages.

A remarkably clear scenario emerges (see the second figure, top panel). The dating rests on 10 externally dated calibration points, of which the more ancient are based on the archaeological data for the Austronesian entry into the Philippines, Micronesia, and Eastern Polynesia (13). The overall scenario, however, derives from the topology of the tree, which does not depend on the archaeology. In the scenario, an Austronesian origin in Taiwan ~5200 years ago was followed by a first pause, and then a major pulse or migration dispersal reaching across the Pacific as far as Micronesia ~3000 years ago. A second pause occurred after the settlement of Western Polynesia around 2800 years ago. A second migration after 1500 years ago led to the peopling of Central and Eastern Polynesia. The level of detail offered by the analysis is impressive, and because the method relies on archaeologically or historically established calibration points, the nodes in the tree--that is, the splitting points resulting from human dispersals--can be dated to within a few centuries.

Support for this picture comes from Moodley et al.'s genetic analysis of samples for the bacterial parasite Helicobacter pylori, taken from the genetic tracts of Pacific human populations. The data also strongly favor a Taiwanese origin, producing a tree (see the second figure, bottom panel) that is similar in many ways to the linguistic tree of Gray et al. The analysis relies on the observation that, although most human populations share a gastric flora of H. pylori, at a molecular genetic level these bacteria differ from continent to continent. These differences are likely to be the product of genetic drift following the splitting and separation of populations. These processes enable reconstruction of a phylogenetic tree similar to that derived from human mitochondrial or Y-chromosome DNA (14). The dates in the bacterial analysis have large error margins and are again derived from archaeologically dependent calibration points. So the fact that both papers date the dispersal from Taiwan to ~5000 years ago is not so much a corroboration but a result of using the same archaeological data. But the topology and detail of the two trees are genuinely independent.

It will be interesting to see how well the topologies of the two trees correlate at a more detailed level, as clearly they do in general structure. The use of modern genetic data to reconstruct phylogenetic trees shows that the past is still "within us" (15) today. Our past is within us in a different sense when the vocabularies of specific modern languages are the basis for historical analysis. And the past is within us in a very literal way when the early history of humankind is reconstructed based on the bacterial flora in our guts. The convergence between the approaches suggests that a synthesis between linguistic and genetic interpretations of human history may soon be possible on a worldwide basis.

I hear the Slovenes are good at building yachts, and like sailing, so you may be interested in the amazing Polynesian migrations as far as New Zealand: 'the bold navigators who, without compass or chart, were sailing the vast spaces of the Pacific a hundred and fifty years before Columbus ventured across the Atlantic'. http://en.wikipedia.org/wiki/Polynesian_navigation

[Major work was done by anthropologist, Te Rangi Hiroa/Sir Peter Buck, mid-last century. I quote from the Foreword to his book, "The Coming of the Maori'.]

Somehow the phrase "Talking sh*t" seems to apply from many different angles to this fascinating info...

An interesting aside - one of the things that allowed the Pacific islanders to populate the vast area was their ability to read wave patterns to identify the positions of islands not even visible from their boats. They could understand wave patterns both by looking at the water surface and by listening to the slap against their hulls. They taught their children the rudiments using frameworks of split, curved bamboo, sort of like an abacus of the waves.

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...Moodley et al.'s genetic analysis of samples for the bacterial parasite Helicobacter pylori, taken from the genetic tracts of Pacific human populations. The data also strongly favor a Taiwanese origin, producing a tree ... that is similar in many ways to the linguistic tree of Gray et al. The analysis relies on the observation that, although most human populations share a gastric flora of H. pylori, at a molecular genetic level these bacteria differ from continent to continent. These differences are likely to be the product of genetic drift following the splitting and separation of populations.

Vito, I was interested in this genetic aspect of the article, particularly after seeing this news report recently.

[In summary: First there were Asian H. pylori groups; then there were hpSahul and hpMaori strains.

Evidence and Inference:

1 ...the hpSahul H. pylori group
a. split off from Asian H. pylori groups between 31,000 and 37,000 years ago. (This likely coincided with migrations to New Guinea and Australia. )
and then
b. A bit later — between 23,000 and 32,000 years ago — the population split again, creating separate hpSahul sub-populations in New Guinea and Australia.

2 the hspMaori strain, on the other hand,
appears to have split off from Asian H. pylori groups more recently. (The researchers' results suggest that the humans who carried these bugs moved from Taiwan, through the Philippines and Melanesia, to Polynesia about 5,000 years ago.)]

That's very interesting!

[Edited at 2009-02-18 01:48 GMT]

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One thing is scientific facts. The other / next thing is the explanation. In the above case I would assume, the whole globe got the same treatment as N. America and Europe - with ice coming down to at least Chicago resp. Alps -. So, yes it is plausible.

Australians would probably appreciate it - at least to a little tiny degree - these days.

Regards

Vito

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